SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6346634019b1d254515877a16a12891c7fcb57857b799687112c2b1aef6c51b8' 
  AND token = '2vUuYKP7cqceegOdEhtGDFTj342VBmMIeypJwlnUAr0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}